JP2009110801A - Cold cathode fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold cathode fluorescent lamp hardly influenced by sputtering even when used in a large tube current. <P>SOLUTION: This cold cathode fluorescent lamp is a cold cathode fluorescent lamp for sealing at least inert gas and mercury gas in an airtightly sealed inside space, and having a pair of cylindrical electrodes 7 forming a bottom surface part 8 on one end and an opening part 10 on the other end, that is, the pair of cylindrical electrodes 7 arranged so that the mutual opening parts 10 are opposed, in a glass tube (unillustrated) forming a phosphor layer on an inner wall surface. The cylindrical electrodes 7 are formed by using molybdenum or a molybdenum alloy as a base material, and the thickness of a wall member of the cylindrical electrodes 7 is set to 0.23-0.36 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cold cathode fluorescent lamp.

  Compared to hot cathode fluorescent lamps, cold cathode fluorescent lamps are easy to miniaturize due to their simple electrode structure, and do not require heating during lighting, so they consume less power and have a longer life because there is no filament breakage. It has the following features. Therefore, cold cathode fluorescent lamps are frequently used in recent years for backlights for liquid crystal display devices such as televisions and monitors. In general, a cold cathode fluorescent lamp is arranged such that a pair of electrodes are opposed to both ends inside a glass tube filled with an inert gas such as argon and mercury gas, and a lead wire is connected to each electrode. .

  The electrode is usually made of nickel (Ni) or a nickel alloy. As materials used for electrodes, nickel is 99.7% by weight, manganese is 0.1% by weight, iron is 0.1% by weight, and other impurities (carbon, silicon, copper, sulfur, etc.) are 0.1% by weight. There are those with the composition ratio.

  The electrode has a cylindrical shape, and is formed in a so-called cup shape so that one end is a bottom surface and the other end is an opening. By forming the electrode in a cylindrical shape, the hollow effect is generated, so that the cathode fall voltage that does not contribute to light emission can be reduced. Therefore, by using the cylindrical electrode, it is possible to improve the light emission efficiency and reduce the power consumption as compared with the case of using a rod-like or plate-like electrode.

  The cylindrical electrodes are respectively arranged slightly inside from both ends inside the glass tube so that the openings face each other. When a voltage is applied between the cylindrical electrodes via the lead wire, electrons are emitted from one cylindrical electrode, and ultraviolet rays are generated by the collision of the electrons with mercury atoms. The ultraviolet rays are converted into visible light by a phosphor layer formed on the inner surface of the glass tube and emitted from the inside of the glass tube to the outside.

  When the cold cathode fluorescent lamp is turned on, the mercury or inert gas ions inside the glass tube collide with the surface of the cylindrical electrode, so that nickel atoms on the surface of the cylindrical electrode are knocked out and scattered. This phenomenon is called sputtering. The cylindrical electrode is consumed due to the scattering of the nickel atoms, but at the same time, the scattered nickel atoms take in the mercury gas and become mercury amalgam, so that the effective amount of the mercury gas decreases. As described above, sputtering consumes the cylindrical electrode of the cold cathode fluorescent lamp and mercury gas, which is a major cause of shortening the lifetime of the cold cathode fluorescent lamp.

  In a cold cathode fluorescent lamp equipped with a cylindrical electrode, by increasing the surface area inside the cylindrical electrode, the current density in the cylindrical electrode when the cold cathode fluorescent lamp is turned on can be reduced. Since the load on the cylindrical electrode due to is reduced, it is possible to extend the life of the cylindrical electrode. Further, when the surface area inside the cylindrical electrode is increased, the hollow effect is more effectively generated in the cylindrical electrode, so that the luminous efficiency of the cold cathode fluorescent lamp can be improved. Therefore, in order to increase the inner surface area of the cylindrical electrode, the thickness of the wall member of the cylindrical electrode is reduced. The thickness of the wall member of the cylindrical electrode is usually formed to be 0.15 mm or less, and the bottom portion which is easily consumed by sputtering when the cold cathode fluorescent lamp is turned on is usually formed to 0.2 mm or less.

  Advantages of using nickel as a raw material for cylindrical electrodes include low cost, good weldability with Kovar, which is generally used as lead wires, and workability such as rolling and drawing. Since it is excellent, it can be easily processed into a cylindrical shape. Further, the nickel cylindrical electrode has sufficient sputtering resistance when used at a tube current of 6 to 7 mA.

  However, with the recent increase in screen size and brightness of liquid crystal display devices, they are increasingly used at tube currents greater than 7 mA, and electrodes corresponding to these are required. When the cold cathode fluorescent lamp is used at a tube current larger than 7 mA, the nickel cylindrical electrode has insufficient sputtering resistance, and the cylindrical electrode and mercury gas are rapidly consumed. Thus, the cylindrical electrode made of nickel has a problem that the cold cathode fluorescent lamp has a short life when the cold cathode fluorescent lamp is used with a large current.

  Therefore, in recent years, a technique for extending the life of a cold cathode fluorescent lamp by using an electrode excellent in sputtering resistance has been studied. Specifically, a cylindrical electrode using molybdenum (Mo) or niobium (Nb), which has a higher melting point and superior sputtering resistance compared to nickel, has been tried.

Conventional techniques of a cold cathode fluorescent lamp using molybdenum or niobium as a cylindrical electrode are disclosed in Patent Document 1 and Patent Document 2.
JP 2002-358922 A JP 2003-187740 A

  In order to form molybdenum for use as a cylindrical electrode, it is necessary to first make the molybdenum raw material into a thin plate. Therefore, after the molybdenum raw material powder is rolled to a solidified sintered body, it is formed into a cylindrical shape. It is drawn. Nickel has a face-centered cubic lattice and is easy to roll at room temperature. However, molybdenum has a body-centered cubic lattice and is difficult to roll at room temperature. Heating is performed when the bonded body is rolled.

  Therefore, for example, when there are crystal grain boundaries where the bonds between the crystals in the sintered body are weak or when the temperature during rolling is not sufficiently high, the surface of the electrode material is fine during rolling or drawing. Cracks may occur. Since the cylindrical electrode with cracks on the surface has a significantly larger area that collides with mercury or inert gas ions inside the glass tube than the cylindrical electrode with no cracks on the surface, the cold cathode fluorescent lamp can be turned on. Sometimes it can be significantly consumed by sputtering. Thus, the occurrence of fine cracks on the surface of the electrode material during rolling or drawing may cause a shortened life of the cold cathode fluorescent lamp.

  Accordingly, an object of the present invention is to provide a cold cathode fluorescent lamp which is not easily affected by sputtering even when used with a large tube current.

  In order to achieve the above object, a cold cathode fluorescent lamp of the present invention includes a glass tube in which at least an inert gas and a mercury gas are sealed in an airtightly sealed internal space, and a phosphor layer is formed on an inner wall surface. A pair of cylindrical electrodes disposed in the internal space, having a bottom surface at one end and an opening at the other end, the pair of cylindrical electrodes disposed so that the openings face each other; A cold cathode fluorescent lamp having one end bonded to the outer surface of the bottom surface portion and the other end led to the outside of the glass tube, wherein the cylindrical electrode is made of molybdenum or a molybdenum alloy as a base material The thickness of the wall member constituting the cylindrical electrode is 0.23 mm or more and 0.36 mm or less.

  According to the present invention, it is possible to provide a cold cathode fluorescent lamp which is not easily affected by sputtering even when used with a large tube current.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view in the longitudinal direction of a cold cathode fluorescent lamp according to an embodiment of the present invention.

  The cold cathode fluorescent lamp 1 includes an airtightly sealed glass tube 2, a bead glass 3 that seals both ends of the glass tube 2, and a pair of electrode units 6 that generate discharge inside the glass tube 2. ,have.

  In the cold cathode fluorescent lamp 1, both ends of a glass tube 2 formed of borosilicate glass are hermetically sealed with bead glass 3. The material of the glass tube 2 may be lead glass, soda glass, low lead glass, or the like.

  The inner wall surface 4 of the glass tube 2 is provided with a phosphor layer (not shown) over almost the entire length thereof. Examples of the phosphor constituting the phosphor layer include phosphors such as halophosphate phosphors and rare earth phosphors, and two or more phosphors may be mixed. These phosphor types can be selected according to the purpose and application of the cold cathode fluorescent lamp.

  A predetermined amount of inert gas such as argon, xenon, neon and mercury is enclosed in the internal space 5 of the glass tube 2 surrounded by the inner wall surface 4, and the internal pressure of the internal space 5 is several tenths of atmospheric pressure. The pressure is reduced to a certain degree. For this reason, the mercury enclosed in the glass tube 2 exists as a gas.

  A pair of electrode units 6 are provided at both ends of the glass tube 2. Each electrode unit 6 includes a cylindrical electrode 7 and a lead wire 9 bonded to the bottom surface portion 8 of the cylindrical electrode 7. The cylindrical electrode 7 of each electrode unit 6 has an opening 10 of one cylindrical electrode 7 and an opening 10 of the other cylindrical electrode 7 at a position slightly inside the end of the internal space 5 of the glass tube 2. Are arranged so as to face each other. One end of each lead wire 9 is joined to the bottom surface portion 8 of the cylindrical electrode 7, and the other end penetrates the bead glass 3 and is drawn out of the glass tube 2. The lead wire 9 is made of a conductive material such as Kovar.

  FIG. 2 is a perspective view of an electrode unit of the cold cathode fluorescent lamp according to the present embodiment.

  The cylindrical electrode 7 includes a cylindrical portion 11 having one end portion in the longitudinal direction opened as an opening portion 10 and the other end portion closed by a bottom surface portion 8. One end surface 12 of the lead wire 9 is welded to the outer surface of the bottom surface portion 8 of the cylindrical electrode 7.

  FIG. 3 is a cross-sectional view in the longitudinal direction of the cylindrical electrode of the cold cathode fluorescent lamp according to this embodiment.

  The cylindrical electrode 7 is formed into a cylindrical shape by rolling a sintered body obtained by solidifying and molding molybdenum or a molybdenum alloy powder mainly containing molybdenum into a thin plate and further drawing.

  The cylindrical electrode 7 has a wall member thickness A of the bottom surface 8 of 0.30 mm, a wall member thickness B of the cylindrical member 11 of 0.28 mm, an outer diameter C of 2.1 mm, and a length in the longitudinal direction. It is molded so that D is 50 mm. While the thickness of the wall member of the cylindrical electrode of the conventional cold cathode fluorescent lamp is usually 0.2 mm or less, the thickness of the wall member of the cylindrical electrode 7 of the cold cathode fluorescent lamp 1 is made thicker than that. ing. This is to reduce the load applied to the crystal grain boundaries of the molybdenum sintered body during rolling or drawing, and the cylindrical electrode 7 is rolled to a thickness of 0.2 mm or less. Compared to the case, generation of fine cracks on the electrode material surface during rolling or drawing can be suppressed.

  It is molded by the same processing method as the cylindrical electrode 7 and has the same outer diameter and length as the cylindrical electrode 7, but the wall member thickness of the bottom surface portion is 0.2 mm and the wall member thickness of the cylindrical portion is the same. In the cold cathode fluorescent lamp using a cylindrical electrode having a length of 0.18 mm, a lot of sputtering occurred during lighting. In comparison, the cold cathode fluorescent lamp 1 using the cylindrical electrode 7 was significantly suppressed from sputtering during lighting. This is because the occurrence of fine cracks on the electrode material surface during rolling or drawing during the production of the cylindrical electrode was greatly suppressed by increasing the thickness of the wall member of the cylindrical electrode. This is an effect obtained as a result.

  The cracks on the surface of the cylindrical electrode increase sharply when the thickness of the wall member of the cylindrical electrode is less than 0.23 mm with a boundary of 0.23 mm, and greatly increase when the thickness is 0.23 mm or more. Diminished. In addition, in the cold cathode fluorescent lamp using the cylindrical electrode having a wall member thickness of less than 0.23 mm, a large amount of sputtering occurs during lighting, whereas the wall electrode thickness is 0.23 mm or more. In the cold cathode fluorescent lamp using, sputtering during lighting was suppressed. As described above, when the thickness of the wall member of the cylindrical electrode is set to 0.23 mm or more, generation of fine cracks on the surface of the electrode material during the rolling process or drawing process when the cylindrical electrode is manufactured. Can be suppressed.

  In addition, by making the thickness of the wall member of the cylindrical electrode 0.28 mm or more, generation of fine cracks on the electrode material surface during rolling or drawing is further suppressed, and the cold cathode fluorescent lamp is turned on. Sputtering at the time was further suppressed.

  As described above, according to the cold cathode fluorescent lamp of this embodiment, since the consumption of the cylindrical electrode due to sputtering can be suppressed, the cold cathode fluorescent light which is not easily affected by sputtering even when used with a large tube current. A lamp can be provided.

  Further, in a cylindrical electrode having a length in the longitudinal direction of 3.8 mm to 11.2 mm, a portion from the outer surface of the bottom surface of the cylindrical electrode to 2.8 mm in the longitudinal direction is easily affected by sputtering and is consumed. It is early to be done. As a result, there is a problem that the cold cathode fluorescent lamp may reach the end of its life due to consumption of this portion of the cylindrical electrode. This problem can be solved by further increasing the thickness of the wall member in this part so that the cylindrical electrode functions normally even if this part is consumed much.

  When the thickness of the wall member of the tubular electrode having a length in the longitudinal direction of 3.8 mm to 11.2 mm and extending from the outer surface of the bottom surface portion to 2.8 mm in the longitudinal direction is less than 0.28 mm, Since the portion is consumed by sputtering faster than the other portions, the cold cathode fluorescent lamp may reach the end of its life due to the consumption of this portion. On the other hand, if the thickness of the wall member in this portion is 0.28 mm or more, the lifetime of the cold cathode fluorescent lamp is greatly reduced due to the consumption due to sputtering in this portion. Thus, in the cylindrical electrode having a length in the longitudinal direction of 3.8 mm to 11.2 mm, the thickness of the wall member of the portion from the outer surface of the bottom surface portion of the cylindrical electrode to 2.8 mm in the longitudinal direction is reduced to 0. By setting the thickness to 28 mm or more, the life of the cold cathode fluorescent lamp can be extended.

  As described above, according to the cold cathode fluorescent lamp of the present embodiment, it is possible to prevent the life of the cold cathode fluorescent lamp from being shortened due to the portion of the cylindrical electrode that is susceptible to sputtering, so that a large tube current can be obtained. Even when used, it is possible to provide a cold cathode fluorescent lamp which is not easily affected by sputtering.

  In addition, as the thickness of the wall member of the cylindrical electrode is increased, the generation of fine cracks on the surface of the electrode material during rolling or drawing during the production of the cylindrical electrode is effectively suppressed. However, if it is too thick, the drawability at the time of producing this cylindrical electrode deteriorates, so that the mass productivity of this cylindrical electrode is impaired. Thereby, the manufacturing cost of this cylindrical electrode becomes high.

  Specifically, when the thickness of the wall member of the cylindrical electrode is 0.36 mm or less, the influence on the mass productivity of this cylindrical electrode was small, but when the thickness exceeds 0.36 mm, the cylindrical electrode The mass productivity of this cylindrical electrode was greatly impaired by the rapid deterioration of the drawing workability when producing the electrode. Thus, it can prevent that the manufacturing cost of this cylindrical electrode becomes high by making the thickness of the wall member of a cylindrical electrode into 0.36 mm or less.

  In addition, by making the thickness of the wall member of the cylindrical electrode 0.32 mm or less, sufficient drawing workability when producing this cylindrical electrode can be obtained, and therefore the influence on the mass productivity of this cylindrical electrode. Was hardly seen.

It is sectional drawing in the longitudinal direction of the cold cathode fluorescent lamp which concerns on one Embodiment of this invention. It is a perspective view of the electrode unit of the cold cathode fluorescent lamp shown in FIG. It is sectional drawing in the longitudinal direction of the cylindrical electrode of the electrode unit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cold cathode fluorescent lamp 2 Glass tube 3 Bead glass 4 Inner wall surface 5 Internal space 6 Electrode unit 7 Tubular electrode 8 Bottom surface part 9 Lead wire 10 Opening part 11 Tubular part 12 End surface

Claims (2)

A glass tube in which at least an inert gas and a mercury gas are sealed in an airtightly sealed internal space, and a phosphor layer is formed on an inner wall surface;
A pair of cylindrical electrodes disposed in the internal space, having a bottom portion at one end and an opening formed at the other end, the pair of cylindrical electrodes disposed so that the openings face each other;
One end is joined to the outer surface of the bottom portion, and the other end is drawn out of the glass tube, and a lead wire,
In a cold cathode fluorescent lamp having
The cylindrical electrode is based on molybdenum or a molybdenum alloy,
The cold cathode fluorescent lamp characterized in that the wall member constituting the cylindrical electrode has a thickness of 0.23 mm to 0.36 mm. The longitudinal length of the cylindrical electrode is in the range of 3.8 mm to 11.2 mm,
The thickness of the said wall member in the part from the outer surface of the said bottom face part to the position of 2.8 mm in the longitudinal direction of the said cylindrical electrode of the said cylindrical electrode is 0.28 mm or more and 0.36 mm or less. 2. The cold cathode fluorescent lamp according to 1.

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